DESCRIPTION: There is growing recognition that women who experience psychological and social adversity during pregnancy (i.e., prenatal stress) are at increased risk for preterm delivery, even after adjusting for the effects of established biomedical and sociodemographic factors. Studies have examined features of stressors or sociodemographic characteristics to identify factors associated with increased vulnerability to stress; however, with one exception, none of these has examined individual differences in women's biological response to stress. The objective of this proposal is to examine the role of maternal biological stress reactivity in outcomes related to the length of gestation. A prospective study will be conducted in sample of at least 200 women to assess the responses of the sympathetic-medullary-adrenal axis (i.e., blood pressure, heart rate) and hypothalamic-pituitary-adrenal system (i.e., ACTH, cortisol levels) to a standard laboratory-based behavioral stress paradigm at three time-points during gestation (10 to 12, 20 to 22, and 30 to 32 wks). The primary study hypothesis is that greater maternal biological reactivity to stress will predict earlier delivery. Secondary hypotheses include: the effects of maternal biological stress reactivity will be mediated by placental CRH; the magnitude of the biological stress response will decrease with advancing gestational age; and baseline hormonal levels, obstetric risk status, and maternal psychosocial factors will correlate significantly with measures of stress reactivity. Significance and implications of this work include identification of the biologic mechanisms which mediate the relation between stress and preterm birth as well as potential development of a prognostic risk assessment for preterm delivery.